A synoptic decomposition of rainfall over the Cape south coast of South Africa
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Date
Authors
Engelbrecht, Christina Johanna
Landman, Willem Adolf
Engelbrecht, Francois Alwyn
Malherbe, Johan
Journal Title
Journal ISSN
Volume Title
Publisher
Springer
Abstract
A synoptic climatology is derived for the
Cape south coast region of South Africa by application
of the self-organizing map (SOM) technique. The SOM
is applied to average daily low-level circulation fields, as
represented by sea-level pressure anomalies for the period
1979–2011. This coastal region receives rainfall all-year
round with slight peaks during March–April and with more
pronounced peaks during August and October–November.
The synoptic forcing responsible for this annual multimodal
rainfall distribution is identified, and the relative
contribution of different synoptic types to the annual rainfall
is quantified. Ridging high pressure systems contribute
to 46 % of the annual rainfall, while tropical–temperate
troughs contribute 28 %. Cut-off lows (COLs) co-occurring
with ridging highs and tropical–temperate troughs are associated
with 16 % of the annual rainfall total. The contribution
of ridging high pressure systems decreases from south
to north, whilst the opposite is true for tropical–temperate
troughs. COLs, ridging high pressure systems and tropical–
temperate troughs are associated with the March–April
rainfall peak, while COLs are largely associated with the August rainfall peak. Ridging high pressure systems and to
a lesser extent tropical–temperate troughs, are responsible
for the October peak observed along the coast, while the
November peak over the adjacent interior regions is associated
with COLs that occur in combination with the tropical–
temperate troughs during this month.
Description
Keywords
All-year rainfall region, Cape south coast of South Africa, Synoptic types, Ridging high pressure systems, Cut-off lows (COLs)
Sustainable Development Goals
Citation
Engelbrecht, CJ, Landman, WA, Engelbrecht, FA & Malherbe, J 2015, 'A synoptic decomposition of rainfall over the Cape south coast of South Africa', Climate Dynamics, vol. 44, no. 9-10, pp. 2589-2607.